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The salient property of the electronic band structure of twisted bilayer graphene (TBG), at the so-called magic angle (MA), is the emergence of flat bands around the charge neutrality point. These bands are associated with the observed…

Mesoscale and Nanoscale Physics · Physics 2023-09-04 Sonia Haddad , Takeo Kato , Jihang Zhu , Lassaad Mandhour

Recent mean-field calculations suggest that the superconducting state of twisted bilayer graphene exhibits either a nematic order or a spontaneous breakdown of the time-reversal symmetry. The two-dimensional character of the material and…

Strongly Correlated Electrons · Physics 2023-03-10 Ilaria Maccari , Johan Carlström , Egor Babaev

When twisted to angles near 1{\deg}, graphene multilayers provide a new window on electron correlation physics by hosting gate-tuneable strongly-correlated states, including insulators, superconductors, and unusual magnets. Here we report…

Twisted graphene bilayers (TGBs) have low-energy van Hove singularities (VHSs) that are strongly localized around AA-stacked regions of the moire pattern. Therefore, they exhibit novel many-body electronic states, such as Mott-like…

Mesoscale and Nanoscale Physics · Physics 2019-05-15 Yi-Wen Liu , Jia-Bin Qiao , Chao Yan , Yu Zhang , Si-Yu Li , Lin He

The emergence of alternating twist multilayer graphene (ATMG) as a generalization of twisted bilayer graphene (TBG) raises the question - in what important ways do these systems differ? Here, we utilize ab-initio relaxation and…

Strongly Correlated Electrons · Physics 2021-11-24 Patrick J. Ledwith , Eslam Khalaf , Ziyan Zhu , Stephen Carr , Efthimios Kaxiras , Ashvin Vishwanath

Ever since the initial experimental observation of correlated insulators and superconductivity in the flat Dirac bands of magic angle twisted bilayer graphene, a search for the microscopic description that explains its strong electronic…

We study the electron-phonon coupling in twisted bilayer graphene (TBG), which was recently experimentally observed to exhibit superconductivity around the magic twist angle $\theta\approx 1.05^\circ$. We show that phonon-mediated electron…

Mesoscale and Nanoscale Physics · Physics 2019-07-03 Biao Lian , Zhijun Wang , B. Andrei Bernevig

A model binary hybrid system composed of a randomly distributed rare-earth ferromagnetic (Gd) part embedded in an s-wave superconducting (Nb) matrix is being manufactured to study the interplay between competing superconducting and…

Superconductivity · Physics 2016-01-06 Ambika Bawa , Anurag Gupta , Sandeep Singh , V. P. S. Awana , Sangeeta Sahoo

We present a theory of superconductivity in twisted bilayer graphene in which attraction is generated between electrons on the same honeycomb sublattice when the system is close to a sublattice polarization instability. The resulting Cooper…

Mesoscale and Nanoscale Physics · Physics 2022-10-26 Chunli Huang , Nemin Wei , Wei Qin , Allan MacDonald

If the topological insulator Bi$_{2}$Se$_{3}$ is doped with electrons, superconductivity with $T_{{\rm c}}\approx3-4\:{\rm K}$ emerges for a low density of carriers ($n\approx10^{20}{\rm cm}^{-3}$) and with a small ratio of the…

Superconductivity · Physics 2018-05-28 Matthias Hecker , Jörg Schmalian

Spontaneous symmetry breaking plays a pivotal role in many areas of physics, engendering a variety of excitations from sound modes in solids to pions in nuclear physics. Equally important excitations are solitons, nonlinear configurations…

Strongly Correlated Electrons · Physics 2021-05-13 Eslam Khalaf , Shubhayu Chatterjee , Nick Bultinck , Michael P. Zaletel , Ashvin Vishwanath

The interfacial coupling between electrons and magnons in adjacent layers can mediate an attractive electron-electron interaction and induce superconductivity. We consider magic-angle twisted bilayer graphene sandwiched between two…

Superconductivity · Physics 2023-01-20 Bjørnulf Brekke , Asle Sudbø , Arne Brataas

Interactions among electrons create novel many-body quantum phases of matter with wavefunctions that often reflect electronic correlation effects, broken symmetries, and novel collective excitations. A wide range of quantum phases has been…

In bilayer graphene, the phase diagram in the plane of a strain-induced bare nematic term, ${\cal N}_{0}$, and a top-bottom gates voltage imbalance, $U_{0}$, is obtained by solving the gap equation in the random-phase approximation. At…

Strongly Correlated Electrons · Physics 2012-09-26 E. V. Gorbar , V. P. Gusynin , V. A. Miransky , I. A. Shovkovy

The role of nematic order for the mechanism of high-temperature superconductivity is highly debated. In most iron-based superconductors (IBS) the tetragonal symmetry is broken already in the normal state, resulting in orthorhombic lattice…

One of the most remarkable theoretical findings in magic angle twisted bilayer graphene (TBG) is the emergence of ferromagnetic Slater determinants as exact ground states for the interacting Hamiltonian at the chiral limit. This discovery…

Mathematical Physics · Physics 2025-06-02 Simon Becker , Lin Lin , Kevin D. Stubbs

Bilayer graphene (BLG) at the charge neutrality point (CNP) is strongly susceptible to electronic interactions, and expected to undergo a phase transition into a state with spontaneous broken symmetries. By systematically investigating a…

Mesoscale and Nanoscale Physics · Physics 2012-08-01 Wenzhong Bao , Jairo Velasco , Fan Zhang , Lei Jing , Brian Standley , Dmitry Smirnov , Marc Bockrath , Allan MacDonald , Chun Ning Lau

Using scanning probe microscopy and spectroscopy, we explore the spatial symmetry of the electronic wavefunctions of twisted bilayer graphene at the "magic angle" of 1.1 degrees. This small twist angle leads to a long wavelength moir\'e…

Mesoscale and Nanoscale Physics · Physics 2020-08-12 Zhiming Zhang , Rachel Myers , Kenji Watanabe , Takashi Taniguchi , Brian J. LeRoy

The physics of superconductivity in magic-angle twisted bilayer graphene (MATBG) is a topic of keen interest in moir\'e systems research, and it may provide insight into the pairing mechanism of other strongly correlated materials such as…

Magic-angle twisted bilayer graphene (TBG) exhibits a captivating phase diagram as a function of doping, featuring superconductivity and a variety of insulating and magnetic states. The bands host Dirac fermions with a reduced Fermi…

Strongly Correlated Electrons · Physics 2023-08-03 Julian Ingham , Tommy Li , Mathias S. Scheurer , Harley D. Scammell